Saturday, April 23, 2011

EGGcellent Decalcification

This eggperiment is fantastic for finding out what acid can do to calcium. It’s also great as you will be left with something elegant and mystifying.

It is fun to do this as a test.

For this experiment you will need:

2 Raw eggs

2 Glasses

Tap water

Vinegar

Place one egg in each glass. Fill one glass with vinegar and the other with water. Leave them in the glasses for 24 hours.

After 24 hours, carefully take the eggs out of the glasses. Do they look different? Can you predict what has happened and why?

We noticed that the one which was covered with water looked no different. The egg from the vinegar felt much different. In fact it felt a little ‘bouncy’! While our vinegar egg was still wet we rubbed it gently and the shell gradually came away. We were left with an egg which was held together by its membrane but no shell! You can hold this shell-less egg up to the light and see its yoke.

The reason for this is that the acid in the vinegar softens the calcium carbonate (the shell). This process is called decalcification. The membrane doesn’t react to the vinegar in the same way so it remains intact.